1. Technical Field
The present invention relates to a light-emitting device, which performs light emission by electroluminescence, and an electronic apparatus.
2. Related Art
As thin and lightweight light sources, organic electroluminescent diodes (OLED), i.e. electroluminescent (EL) elements have been paid attention, and image displaying devices equipped with a plurality of light-emitting devices such as OLED have been developed. The light-emitting device generally has a structure in which at least one layer of organic thin film made of organic material is interposed between a pixel electrode and an opposing electrode.
In the field of EL devices, WO-A-01/39554 discloses a technique in which a specific wavelength of emitted light is enhanced by amplifying interference such as resonance. With this technique, it is possible to increase color purity and efficiency of emitted light.
However, such an EL device has a problem in that quality of a displayed image deteriorates thanks to the outdoor daylight reflection at the displaying surface. In order to solve this problem, for example, suggested is a technique in which a circularly polarizing plate is disposed at the displaying surface side. However, such a technique still has a problem like the decrease of luminosity since the circularly polarizing plate decreases light emitted from the light-emitting layer.
In addition, Japanese Patent No. 3944906 discloses a method of decreasing the outdoor daylight reflection by arranging color filters and organic EL elements in an overlapping manner. This method is to absorb wavelengths of light other than specific wavelengths supposed to be transmitted through the color filter. However, in this method which simply employs the color filters, reflection of colors of light different from the light emitted from the organic EL elements is decreased but reflection of colors of light which are the same or similar to colors of light emitted form the light-emitting elements is not decreased.
Moreover, Japanese Patent No. 3944906 discloses a technique in which the phase of reflected light of the outdoor daylight at a translucent electrode of an organic EL element and the phase of reflected light of the outdoor daylight at a reflective electrode are opposite to one another.
As disclosed in Japanese Patent No. 3944906, when the phase of reflected light at one surface and the phase of reflected light at another surface are opposite to one another, the reflected light can be decreased thanks to attenuating interference. However, under such condition, there is a limit especially in increasing efficiency of light emitted during light emission. Japanese Patent No. 3944906 discloses an organic EL element including a translucent electrode and a reflective electrode and the structure of a resonator which resonates light by reciprocating the light between the translucent electrode and the reflective electrode. With even the structure in which light reciprocates between electrodes, it is impossible to increase the light usability without resonance of light when optical factors such as an optical distance are appropriate.